Fig. 1: Dexamethasone promotes mitochondria dynamics and enhances kinesin-1 motor activity.
a C2C12 cells treated with DMSO (control), 0.1, 1, or 10 µM Dex in differentiation medium for 1 day or 5 days had their mitochondrial numbers assessed using the ratio of cytochrome C oxidase I DNA (to indicate mitochondrial DNA; mtDNA) to 18S rRNA DNA (to indicate nuclear DNA; nDNA) by real-time PCR. Data are mean ± s.e.m (n = 3 independent experiments). NS no significance (compared with the control). b ATP production rate was calculated from oxygen consumption rate (OCR) in C2C12 cells treated with DMSO (control) or 1 µM Dex for 6 h. OCR was measured continuously followed by the addition of oligomycin (1 µM), Carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP; 1 µM), and antimycin A (0.5 µM) with rotenone (0.5 µM) using Seahorse XFe24 Extracellular Flux Analyzer. Data are mean ± s.e.m (n = 3 independent experiments). *p < 0.05 (compared with control). c C2C12 cells treated with DMSO (control), 0.1 µM Dex, 1 µM Dex, 10 µM Dex for 1 h, or with 10 µM nocodazole for 16 h were stained with MitoTracker Red to visualize mitochondria. Scale bar, 10 µm. d Comparison of the average values for the speed of mitochondrial movement in C2C12 cells. Data are mean ± s.e.m (control, n = 3638 mitochondria/5 cells; 0.1 µM Dex, n = 5016 mitochondria/6 cells; 1 µM Dex, n = 3635 mitochondria/6 cells; 10 µM Dex, n = 4818 mitochondria/6 cells; nocodazole, n = 632 mitochondria/2 cells). ***p < 0.001 (compared with the control). e Time-lapse epi-fluorescence microscopy showing the movement of rhodamine-labeled microtubules treated with control (DMSO) or 1 µM Dex, using in vitro kinesin-1 motility assay. Scale bar, 2 µm. f Comparison of the average values for the speed of microtubule movement brought about by kinesin-1. Data are mean ± s.e.m (control, n = 494 microtubules; 1 µM Dex, n = 370 microtubules). ***p < 0.001 (compared with control).
